[Minor] Mark operators constexpr

diff --git a/src/libmime/mime_string.hxx b/src/libmime/mime_string.hxx
index 890708de20a4f956feda52c71f7089e9483d8eee..41d2f5f7ef5447ee16298d4269f1ca30973f6c09 100644 (file)
--- a/src/libmime/mime_string.hxx
+++ b/src/libmime/mime_string.hxx
@@ -52,19 +52,19 @@ enum class mime_string_flags : std::uint8_t {
        MIME_STRING_SEEN_INVALID = 0x1 << 1,
 };
 
-mime_string_flags operator |(mime_string_flags lhs, mime_string_flags rhs)
+constexpr mime_string_flags operator |(mime_string_flags lhs, mime_string_flags rhs)
 {
        using ut = std::underlying_type<mime_string_flags>::type;
        return static_cast<mime_string_flags>(static_cast<ut>(lhs) | static_cast<ut>(rhs));
 }
 
-mime_string_flags operator &(mime_string_flags lhs, mime_string_flags rhs)
+constexpr mime_string_flags operator &(mime_string_flags lhs, mime_string_flags rhs)
 {
        using ut = std::underlying_type<mime_string_flags>::type;
        return static_cast<mime_string_flags>(static_cast<ut>(lhs) & static_cast<ut>(rhs));
 }
 
-bool operator !(mime_string_flags fl)
+constexpr bool operator !(mime_string_flags fl)
 {
        return fl == mime_string_flags::MIME_STRING_DEFAULT;
 }